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Learning processes in reptiles
... In addition, animal screen touches are registered and relayed back to the system for real-time feedback to the displayed stimuli, or other triggerable arena components. Together, ReptiLearn integrates multiple methodologies for interacting with animals and for delivering rewards with a low latency feedback, which are instrumental for effective learning and conditioning paradigms (49,(59)(60)(61). ...
... Notably, our innovative approach departs from previous spatial essays that necessitated performing an extensive number of trials, each lasting up to tens of minutes (59,74), until performance criteria were met (76). These experiments were usually conducted manually, demanding substantial efforts from experimenters, such as baiting food rewards in each trial (73) or repositioning of animals (74). ...
... Despite pioneering work in the field (59,74,77,78), our understanding of the cognitive abilities of reptiles, and cold blooded animals in general, remains limited. Such research can shed light on the evolution of cognition and provide a comparative perspective critical for generalized understanding (28,(30)(31)(32)(33)(34). ...
Understanding behavior and its evolutionary underpinnings is crucial for unraveling the complexities of brain function. Traditional approaches strive to reduce behavioral complexity by designing short-term, highly constrained behavioral tasks with dichotomous choices in which animals respond to defined external perturbation. In contrast, natural behaviors evolve over multiple time scales and under minimally constrained conditions in which actions are selected through bi-directional interactions with the environment and without human intervention. Recent technological advancements have opened up new possibilities for more natural experimental designs by replacing stringent experimental control with accurate multidimensional behavioral analysis. However, these approaches have been tailored to fit only a small number of species. This specificity limits the experimental opportunities offered by species diversity. Further, it hampers comparative analyses which are essential for extracting overarching behavioral principles and for examining behavior from an evolutionary perspective. To address this limitation, we developed ReptiLearn - a versatile, low-cost, Python-based solution, optimized for conducting automated long-term experiments in the home cage of reptiles, without human intervention. In addition, this system offers unique features such as precise temperature measurement and control, live prey reward dispensers, engagement with touch screens, and remote control through a user-friendly web interface. Finally, ReptiLearn incorporates low-latency closed-loop feedback allowing bi-directional interactions between animals and their environments. Thus, ReptiLearn provides a comprehensive solution for researchers studying behavior in ectotherms and beyond, bridging the gap between constrained laboratory settings and natural behavior in non-conventional model systems. We demonstrate the capabilities of ReptiLearn by automatically training the lizard Pogona vitticeps on a complex spatial learning task requiring association learning, displaced reward learning and reversal learning.
... Most studies on learning capacities in crocodylians date back to the middle of the last century. An excellent overview of this literature was provided by Burghardt (1977) and an update by Sazbo et al. (2019). ...
... Caimans reduced their proportion of choices of a side with a decreasing probability of that side being rewarded. Their performance was more similar to turtles and rats than to birds in contemporary studies (Burghardt 1977;Williams and Albiniak 1972). ...
... Most studies on learning capacities in crocodylians date back to the middle of the last century. An excellent overview of this literature was provided by Burghardt (1977) and an update by Sazbo et al. (2019). ...
... Caimans reduced their proportion of choices of a side with a decreasing probability of that side being rewarded. Their performance was more similar to turtles and rats than to birds in contemporary studies (Burghardt 1977;Williams and Albiniak 1972). ...
... hue). In his comprehensive review of learning processes in reptiles, Burghardt (1977), listed 12 such studies, of which half involved some type of hue discrimination, and more have been published in the ensuing decades. These studies have shown that lizards can discriminate between stimuli differing only in hue (e.g. ...
... hue). In his comprehensive review of learning processes in reptiles, Burghardt (1977) listed 12 such studies, of which half involved some type of hue discrimination, and more have been published in the ensuing decades. These studies have shown that lizards can discriminate between stimuli differing only in hue (e.g. ...
Colour polymorphisms, the coexistence of two or more colour morphs of a species within a population, have long fascinated evolutionary biologists interested in the mechanisms generating and maintaining phenotypic variation in nature. The functional significance of colour polymorphisms (i.e. their adaptive value) is often linked to the selective mechanisms responsible for their maintenance over time. In lizards, the hypothesis that colour morphs may reflect alternative reproductive strategies involving differential sociosexual behaviour and/or alternative reproductive strategies has come to dominate the field. Wall lizards (family Lacertidae, genus Podarcis), with several geographically distant species that exhibit two or more alternative ventral colour morphs, have often been identified as a group in which alternative reproductive strategies and frequency-dependent selection likely underpin colour polymorphisms. However, several key aspects regarding the link between behaviour, fitness, and lacertid colour polymorphism remain overlooked or inadequately studied. In this thesis we tried to fill these gaps by experimentally addressing some of the most commonly assumed ideas about the functional significance of colour polymorphism in the European common wall lizard (Podarcis muralis, Laurenti 1768). In some populations of this species (e.g. eastern Pyrenees), adult lizards of both sexes may show up to three “pure” alternative colour morph (orange, white, yellow), and two mixed morphs consisting of a mosaic of differently-coloured scales (orange-white, yellow-orange). Although colour morphs are frequently thought to function as social signals mediating intraspecific interactions, morph categorization has been never assessed from the viewpoint of the intended receivers (i.e. conspecifics). Here, using a discrimination experiment and visual modelling, we found that lizards likely perceive the alternative colour morphs as chromatically distinct and show evidence of discriminating among them based on hue, rather than luminance. To evaluate the role of male coloration (including alternative colour morphs) in intra-sexual competition), we conducted lab-staged dyadic contests among size-matched males. We found lower fighting ability in lizards showing a smaller fraction of their outer ventral scales covered with dark melanin-based spots, and in lizards with orange ventral colour (which could result from the existence of a subordinate non-territorial strategy in this morph). However, our results in later studies (with a free-ranging population and ten experimental mesocosm enclosures), strongly refute the hypothesis that alternative socio-sexual behaviour or space use strategies characterize colour morphs when lizards interact under more natural conditions. In the free-ranging populations, colour morphs did not differ in inter-annual site-fidelity, home-range size, or male-female overlap. In the mesocosm enclosures, spatial dominance was the prime determinant of male fitness across colour morphs. In a later experiment, we conducted controlled matings among pure colour morphs and found no overall effect of female morph on clutch size or juvenile mass, and no effect of morph combination on offspring viability or prospective fitness. These results refute the existence of alternative reproductive strategies in female morphs and are also in disagreement with predictions from both correlational selection and heterosis. Lastly, by keeping the juveniles of known crosses in outdoor enclosures for a year, we studied the inheritance and ontogeny of P. muralis colour polymorphism. Specifically, our results confirmed that orange and yellow colour expression depends on two recessive alleles located at two separate autosomal loci and revealed that the whitish coloration exhibited by newborn lizards is likely perceived by conspecifics as a chromatically distinct colour different from any of the morph colours expressed by adult lizards. Overall, in this thesis we have hopefully presented compelling arguments to revise our perspective on the functional significance of lacertid colour polymorphisms, suggested promising lines of research for future work, and generally contributed to our understanding of the processes maintaining intra-specific variation in natural populations at large.
... Cognition can also affect fitness, as it can mediate reproductive behavior, foraging, defense, spatial distribution, and migration (Shettleworth, 2010). The first comprehensive review on learning in reptiles was written 46 years ago (Burghardt, 1977), and a recent one (Szabo et al., 2021) provides an extensive overview SNAKES: SLITHERING FROM SENSORY PHYSIOLOGY TO COGNITION of reptilian learning abilities and essentially serves as an update of the former. ...
... Gordon Burghardt (1977) wrote the first major review of reptile learning. He reviewed an impressive amount of literature and criticized the then prevailing view that reptiles are instinct-driven and incapable of learning, pointing out important limitations in previous studies. ...
... Although the subjects were only allowed to take a roundabout walking route without the goal in sight, instead of a direct jump to reach the target, they still had a high success rate. Many species have been studied in various detour experiments, where their success rates showed an association with the assumed evolutionary need to be adapted, for solving this type of problem ( [17]; canids: [12,18,19]; great apes: [20]; monkeys: [21]; reptiles: [22]). ...
We tested companion cats and dogs in similar indoor conditions using identical procedures in the classic detour task around a V-shaped transparent wire-mesh fence. Besides the control group, we used two types of laser light-pointing demonstration (moving around the fence, or pointing straight at the reward). We found that dogs reached the food reward faster than cats; across consecutive trials, only the dogs showed improvement in their speed and dogs continued to use the same side for detouring after a preceding successful attempt, while cats chose the side for detouring irrespective of their previous successful trials. In addition, ‘demonstrating’ a detour with the laser did not influence the speed or direction of the detour of the subjects; and dogs looked back to their owner more frequently than the cats did. We discuss the possibility that for dogs, detouring along a transparent obstacle represents a more problematic task than for cats; therefore, dogs strongly rely on their previous experiences. This is the first time that cats were successfully tested in this detour paradigm in direct comparison with dogs. The results are relevant from the aspect of testing cognitive performance in companion cats, which are known to be notoriously reluctant to engage with novel experimental situations.
Zoos and aquaria are paying increasing attention to environmental enrichment, which has proven an effective tool for the improvement of animal welfare. However, several ongoing issues have hampered progress in environmental enrichment research. Foremost among these is the taxonomic bias, which hinders our understanding of the value of enrichment for neglected groups, such as reptiles. In this study, we evaluated the status of environmental enrichment for reptiles in European zoos using a survey approach. A total of 121 zoos (32% response rate) completed our main survey, focusing on the use of different enrichment types for reptiles. We found significant differences in the use and/or type of enrichment between reptile groups. Tortoises (family Testudinidae) and monitor lizards (genus Varanus) were the most enriched taxa while venomous snakes were the least. The enrichment types most used across taxa were structural/habitat design and dietary. A second, more detailed, questionnaire followed, where participants were questioned about specific enrichment techniques. A total of 42 enrichment methods were reported, with two being represented across all taxa: increasing structural/thermal complexity and enrichment objects. Finally, we present information from participating zoos on enrichment goals, assessment methods, sources of information for enrichment ideas, and whether enrichment for reptiles is considered essential and/or implemented routinely. Results suggest that, although usage is widespread across European zoos, our understanding of enrichment for reptiles needs to be re-evaluated, since many of the techniques reported tread a fine line between basic husbandry and actual enrichment.
Despite abundant evidence to the contrary, non-avian reptiles are widely considered as behavioural and cognitive underachievers. The persistent myth of the sluggish, primitive, stupid reptile can be traced, at least in part, to long-standing misconceptions about reptilian brain size and organisation. Historically, reptile brains have been considered small and lacking the neural structures that support complex cognition in other vertebrates. In particular, the notion that reptiles lack a cerebral cortex has led to expectations that their behaviour and cognition should be simple and unsophisticated in comparison with birds and mammals. However, it was shown several decades ago that reptiles possess a large pallium comprising three–four distinct cortical areas and a dorsal ventricular ridge that may be functionally equivalent to parts of mammalian neocortex. In fact, forebrain organisation conforms to a common plan in birds and reptiles, which may seem surprising given the recent trend to put the cognitive achievements of birds above those of reptiles yet on a par with mammals. Moreover, the view that reptiles do not exhibit complex cognition faces a growing list of exceptions. Reptiles are capable of spatial, social, reversal, problem-solving, and many other types of learning and cognitively demanding behaviours provided that experimental designs account for some peculiarities of their biology involving their morphology, physiology, and ecology. Unlike frequent caricatures that depict reptiles as clumsy, inflexible, and instinct-driven, much reptile behaviour is precisely performed, delicate in appearance, readily modified, and contextually determined. Recent work has shown that reptiles can show elaborate communication and social systems, parental care, social learning, and play. Although such research is sparse compared to endothermic vertebrates, and the diversity among them immense, captive reptiles also benefit from enrichment, recognise their caretakers individually and form bonds with them, and are affected by early social isolation in ways similar to birds and mammals. Still, the gap between what we know and what we would like to know about reptilian behaviour and cognition is enormous.KeywordsBrainBrain sizeCerebral cortexCognitionLearningBehaviourComplex behaviourSocial behaviourParental carePlay
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